1. Field
The present invention relates to a frequency adjusting technology, and more specifically, to a frequency adjusting circuit and method in an AC direct lighting apparatus, capable of adjusting a frequency of an output current even when an input voltage is changed.
2. Description of the Related Art
Light Emitting Diode (LED) lighting equipment may reduce power consumption compared to other known light sources in the art while still producing a similar amount of illumination. Accordingly, the LED lighting equipment may be used as a substitute or in addition to conventional lighting fixtures. Some LED lighting equipment has adopted the use and implementation of an AC direct driving circuit and are therefore capable of using an AC voltage directly, rather than a DC voltage.
Such an AC direct driving circuit may improve weight and spatial requirements of the LED lighting equipment. However, a frequency of the driving current may change when a reference voltage changes. Further, when sensing a peak value of the driving current in order to adjust the frequency of the driving current, a voltage spike may occur due to a turn-on or turn-off of a switch. Therefore, because of the voltage spike, it may not be possible to sense the driving current precisely.
In the AC direct driving circuit, a frequency fluctuation of the driving current may make it difficult to match timings of an input current and an output current. When a timing of the input current is mismatched with that of the output current, there occurs a reactive power, increasing a power loss of the LED lighting equipment.